Advancements in cosmology in the twentieth century

Hubble's Law (1929): Edwin Hubble's observations provided evidence for the expansion of the universe. He observed that galaxies are moving away from us, and the farther a galaxy is, the faster it is moving away. This led to the formulation of Hubble's Law, indicating the expansion of the universe.

Big Bang Theory (1927-1948): Building upon the expanding universe concept, scientists like Georges Lemaître and George Gamow developed the Big Bang Theory. This theory proposes that the universe began from an extremely hot and dense state and has been expanding ever since.

Cosmic Microwave Background (CMB) Radiation (1964): Arno Penzias and Robert Wilson accidentally discovered the Cosmic Microwave Background, which is the faint radiation left over from the Big Bang. This discovery provided strong support for the Big Bang Theory.

Inflationary Cosmology (1980s): Proposed by Alan Guth and others, the inflationary model suggests a brief period of exponential expansion in the early universe. This model helps address certain issues with the standard Big Bang model, providing a more comprehensive explanation for the large-scale structure of the universe.

Dark Matter (1930s-1970s): While the concept of dark matter was introduced in the 1930s, it gained significant attention in the latter half of the twentieth century. Observations of galaxy rotation curves and cosmic microwave background fluctuations provided evidence for the existence of non-luminous, or dark, matter.

Dark Energy (1998): The discovery of the accelerating expansion of the universe, based on observations of distant supernovae, led to the proposal of dark energy. Dark energy is thought to be responsible for the accelerated expansion, but its nature remains one of the biggest mysteries in cosmology.